Heat transfer characteristics and compatibility of molten salt/ceramic porous composite phase change material

Abstract

Molten salts are popular energy storage materials for medium- and high-temperature thermal energy storage. However, current methods for heat transfer enhancement do not apply due to the high corrosivity of molten salts and extreme high-temperature environment. Herein, porous silicon carbide (SiC) ceramic and solar salt are formed into a composite phase change material (PCM). The ceramic skeleton is fabricated to an open-cell structure with high porosity and a large pore configuration. The SiC ceramic is wetted by the solar salt, so that the impregnation of salt into ceramic achieves a high loading at atmospheric pressure. The result of visual inspection shows that the temperature distribution in the composite PCM is more uniform compared with pure solar salt. The maximum temperature difference is reduced from 148 ℃ to 130 ℃ and the overall phase change rate is increased by up to 42.9 %. The SiC ceramics show excellent corrosion resistance during the cycles of thermal charging and discharging as compared to copper and aluminium which are the widely used thermal promoters for low-temperature PCMs. The results obtained from reactive molecular dynamics (MD) simulation are consistent with the corrosion behaviours of SiC ceramic in solar salt from aspects of physical dissolution, chemical reaction, and thermal stress failure. The composite PCM has advantages of simple preparation, low cost, and easy maintenance, therefore it has a great potential for large-scale applications.